Acute Failure of a Glenoid Component in Anatomic Shoulder Arthroplasty

Conversion of anatomic total shoulder arthroplasty to reverse shoulder arthroplasty using a unique hybrid glenoid component: technique and preliminary results

Background

Degenerative arthritis of the shoulder is a common condition that is successfully treated with anatomic total shoulder arthroplasty (TSA). Rotator cuff disease has evolved as a leading cause of failure of anatomic TSA, requiring revision to reverse shoulder arthroplasty (RSA). This revision procedure can be extremely complex, particularly if removal of a well-fixed glenoid component is necessary. This case series outlines the technique and preliminary clinical results of conversion of anatomic TSA to RSA utilizing both modular humeral and hybrid glenoid components.

Methods

From July 2017 to December 2019, the senior author (PMC) performed 84 consecutive anatomic TSA procedures utilizing a modular humeral arthroplasty system and a unique hybrid glenoid component. Three cases (3/84, or 3.6%) required conversion from anatomic TSA to RSA because of postoperative traumatic rotator cuff failure. All modular revision cases were performed without humeral stem removal and with utilization of the existing, well-fixed hybrid glenoid central titanium peg as the foundation for glenoid component revision. Preoperative and postoperative American Shoulder and Elbow Surgeons scores, visual analog scale pain scores, forward flexion, and patient satisfaction were analyzed in this modular revision group. In addition, several perioperative variables including operative time, blood loss, and length of stay were compared between this modular revision group and a nonmodular anatomic TSA to RSA revision comparative cohort.

Results

At an average follow-up of 24 months, average active forward flexion, postoperative American Shoulder and Elbow Surgeons scores, and visual analog scale pain scores improved significantly compared with preoperative scores in the modular revision group. All three patients were satisfied with their outcome. The average total operative time (109 minutes vs. 154 minutes, P = .02), blood loss (183 cc vs. 500 cc, P = .08), and length of hospital stay (26.3 hours vs. 36.6 hours P < .05) were lower in the modular revision group than those in a nonmodular revision cohort.

Conclusion

Revision of anatomic TSA to RSA utilizing a modular humeral system and a convertible hybrid glenoid component that does not require removal of a well-fixed central titanium peg which serves as the foundation for glenoid component revision was performed efficiently, safely, and successfully in three cases. This technique results in significantly improved clinical outcomes when revision to RSA is needed while potentially decreasing perioperative complications in the revision setting.

Articular surface failure in hybrid anatomic glenoid components: a unique failure mechanism

PURPOSE

Glenoid loosening is a common failure mechanism of anatomic total shoulder arthroplasty (TSA). New hybrid fixation glenoids allow bony ingrowth and decrease the rates of glenoid loosening. The purpose of this study is to describe a new failure mode of polyethylene dissociation from the ingrowth cage in a single implant design.

METHODS

A retrospective review was performed using an institutional shoulder arthroplasty database of a single hybrid cage glenoid (Exactech, Gainesville, FL). Implants demonstrating this failure mechanism were investigated.

RESULTS

Five out of 206 (2.4%) primary TSAs with cage glenoids performed at our institution and 2 referred for revision suffered glenoid articular face failure. Mean age was 57 (range 38-67 years). Two of 7 failures (29%) occurred secondary to trauma. Failure occurred at mean 14 months after index arthroplasty (range 0-30 months). Revision occurred at mean 24 months after index arthroplasty (range 6-39 months). Six of the 7 patients (86%) had posteriorly augmented glenoids. All 6 patients who had available pre-failure radiographs demonstrated off-axis deviation between the peripheral pegs and central cage (mean 4.8°, range 3°-6°), which may predispose the implant to failure by pre-stressing the material interface.

CONCLUSION

Failure between the glenoid articular face and the central ingrowth cage is a unique failure mechanism to modular hybrid ingrowth glenoids. We hypothesize that this is predisposed by off-axis drilling leading to pre-stressing of the material interface. Surgeons should be aware of the existence of this failure mechanism, particularly when seeing patients with acute pain after an otherwise unproblematic TSA.